This invention relates to a slitter apparatus and more specifically to a slitter mounting bracket for an endless web material.
In processing paper it is a usual operation to transform wide-width rolls of paper, as manufactured, into rolls of narrower widths. This is accomplished by a machine referred to in the industry as a slitter which, in the usual installation, longitudinally advances a paper web between opposed sets of rotary knives or a cutting blade and an opposing anvil. The slitting apparatus is generally referred to as the narrow-cut or shear type which is used to trim and cut web material on the web winding machines. This type of slitting apparatus is generally in the form of a thin steel disk manufactured from hardened and tempered tool steel, and peripherally ground to obtain a sharp edge in order to form a circular knife. The disk cooperates with an opposing driven cutter disk or drum and is kept in rotating contact by overlapping and engaging the side of the drum, and the plane of the axis of rotation thereof will normally be at a slight angle with respect to the axis of rotation of the cooperating drum to form a shear angle. The blade and drum, while rotating together, must be maintained in contact at an optimum amount of pressure in order to sever a web of material with a consistently clean cut. The necessity for maintaining the optimum shear angle and optimum pressure is well recognized by the prior art and various means have been devised in order to achieve these results, the most common of which being the utilization of spring pressure in order to maintain the required parameters. In addition, depth adjustment of the cutting edge must be maintained cooperating with the spring devices so as to maintain the necessary depth setting, permitting displacement-movement of the cutting edge while maintaining a set tension. In addition, the base mount for the slitter must be such that the proper blade mounting angles are maintained with respect to the corresponding drum or anvil face.
Although the heretonow utilized slitter mechanisms have been found useful in the paper web industry, there are known disadvantages in the use of the present known systems producing nonuniform and inefficient slitting operations. Generally, the currently used mechanisms employ no effective means for controlling the spring tension applied and thus, variable tensions are produced, run to run, resulting in nonuniform, extensive blade and anvil wear producing a rough, dust-prone cut. The accumulation of surface dust generated during the slitter operation is magnified when the resulting paper is used in a printing operation which leads to poor print quality as a result of a phenomenon known as ink-piling. Further, the current depth adjustments are often cumbersome and imprecise and thus contribute to improper blade positioning with respect to the opposing anvil, with the point of cut changing with a change in blade diameter. Tests have determined that optimum slitting can only be achieved by proper blade positioning with respect to the anvil. The change in location of cut, with a change of blade diameter, normally results in additional interference of the blade with the cut paper edge. The screw device used for controlling depth of the cutting edge in one prior art embodiment continually exerts pressure on the surface of the mounting bracket base, resulting in wear to the base surface. In addition, due to the type of movement and pressure exerted on the threads within the bracket housing, stripping almost inevitably occurs. The spring which is positioned between the bracket housing and base undergoes relatively high tension and force due to the weight of the bracket and vibrations encountered during operation. At high machine speeds, when vibration becomes a major concern, movement, particularly that regulated by the depth-spring, becomes quite noticeable thus resulting in imprecise slitting. In many brackets the base mount configurations do not ensure squaring at the blade-anvil interface. Thus, it is possible for the blade to be mounted in a somewhat cocked position resulting in excessive anvil-blade wear producing an ineffective cut.